# Homework Help: PA=LU decomposition

1. Apr 24, 2012

### sid9221

http://dl.dropbox.com/u/33103477/matrix.png [Broken]

This is my work:

$$U=\begin{bmatrix} -3/2 & 3/2 & 5/2 &-13/2\\ 0 & 4 & 4 & -8\\ 0 & 0 & -1 & 2\\ 0 & 0 & 0 & -3 \end{bmatrix}$$

$$L=\begin{bmatrix} 1 & 0 & 0 & 0\\ 2 & 1 & 0 & 0\\ 1/2 & 13/28 & 1 & 0\\ 2/5 & -8/15 & -3/4 & 1 \end{bmatrix}$$

[/tex]

$$P=\begin{bmatrix} 0 & 0 & 0 & 1\\ 0 & 1 & 0 & 0\\ 1 & 0 & 0 & 0\\ 0 & 0 & 1 & 0 \end{bmatrix}$$

I don't quite understand how to work out P, during my partial pivoting I had a R1->R4 and then a R3->R4 so I am guessing the P matrix should be the one above.

Last edited by a moderator: May 5, 2017